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The detection of quality deterioration in fresh agricultural products was recognized as being of great significance for industries such as logistics, transportation, and storage. Fresh agricultural products are highly susceptible to quality deterioration, with ammonia serving as a critical indicator of such changes. To overcome the challenges of complex circuit design and limited lifespan in traditional chip-based ammonia sensors, a chipless radio frequency identification (RFID) ammonia sensor for detecting volatile ammonia in fresh produce was proposed. The sensor design utilized the high frequency structure simulator (HFSS) to develop a microstrip patch antenna, optimizing its electromagnetic properties, return loss, and polarization characteristics. Structural enhancements were achieved by incorporating metal shortcircuits and parasitic elements into the antenna. A sensor tag was fabricated using laser engraving, and ZnO/TiO2 nanocomposite material, known for its excellent ammonia selectivity at room temperature, was applied to the radiating elements of the antenna. A chipless RFID-based testing system was then established to detect volatile ammonia in fresh agricultural products. The sensor’s crosssensitivity to interfering gases and its stability under low-temperature, high-humidity conditions was further evaluated. Principal component analysis (PCA) and Pearson correlation analysis were used to analyze the sensor’s performance in practical applications. Experimental results showed that the chipless RFID ammonia sensor operated with a central resonance frequency of 2.25GHz, achieving a gain improvement of 0.13dB after adding metal short-circuits. In a controlled environment with ammonia concentrations ranging from 0mg/L to 100mg/L, the sensor demonstrated a sensitivity of 0.11dB·L/mg. During practical testing, the sensor exhibited a higher response to chicken (9.0dB) compared with shrimp (4.5dB). Additionally, the sensor displayed strong resistance to interference gases such as H2S, CO2, CH4, and C2H5OH, with absolute correlation coefficients below 0.5. The ammonia detection response was stable under low-temperature, high-humidity conditions and exhibited a monotonic relationship with temperature and humidity. These findings underscored the potential of the chipless RFID ammonia sensor as a robust, cost-effective solution for monitoring volatile ammonia in fresh agricultural products, providing significant theoretical and practical contributions to food quality assurance.